Semiconductor devices and methods of forming a trench in a semiconductor device

ABSTRACT

Semiconductor devices and methods to form a trench in a semiconductor device are disclosed. A disclosed process comprises: forming a hollow by etching a portion of a semiconductor substrate; forming a side wall layer in an inner side wall of the hollow; forming a trench by further etching the semiconductor substrate exposed through the bottom of the hollow; and filling the trench by forming an insulation film on the side wall layer and the trench.

RELATED APPLICATION

This patent arises from a divisional application claiming priority fromU.S. application Ser. No. 10/745,028, filed Dec. 23, 2003.

FIELD OF THE DISCLOSURE

This disclosure relates generally to semiconductor devices, and moreparticularly to methods of forming a trench formed as a field region ina semiconductor device to isolate one active region from another withinsulation material without any voids.

BACKGROUND

STI (shallow trench isolation) structures have been widely used asisolation structures in semiconductor devices. These STI structuresfacilitate the miniaturization of semiconductor devices since the sizeof the field region is limited to a desired size of a trench by formingthe trench in the semiconductor substrate and filling the trench withinsulation material.

Conventionally, in forming a trench isolation structure, a pad oxidefilm is deposited at a thickness of about 200 Å on a semiconductorsubstrate. A silicon nitride film is then deposited on the pad oxidefilm. Subsequently, a photosensitive film is applied and exposed on thesilicon nitride film. The photosensitive film is then formed into apattern by removing only the portion of the photosensitive film coveringthe region to be processed to define the trench.

Next, the trench is formed in the semiconductor substrate by dry etchingthe exposed silicon nitride film, the pad oxide film, and thesemiconductor substrate up to a predetermined depth while using thephotosensitive film pattern as a mask. Subsequently, the photosensitivefilm pattern is removed. A cleaning process is then performed.

Subsequently, a liner oxide film is formed on an entire surface of thesilicon nitride film (including on an inner wall of the trench). Atrench oxide film is then thickly deposited on the liner oxide film suchthat the trench is sufficiently filled.

The trench oxide film is then planarized by a chemical mechanicalpolishing process until the silicon nitride film is exposed. Finally,the silicon nitride film is removed to complete the trench isolationprocess.

In the conventional trench isolation structure, stress is concentratedon an edge of the trench. In addition, this edge of the trench is likelyhollowed since the liner oxide film and a portion of the trench oxidefilm are etched together when the silicon nitride film is wet etched.This may make the edge of the trench fragile.

Moreover, as semiconductor devices become more and more integrated,contacts become more susceptible to misalignment with the fragile edgeof the trench. This misalignment may cause leakage current due tocontact spiking, which may cause fatal defects in the semiconductordevice.

Conventional techniques for preventing this leakage current of thetrench due to misalignment of the contacts are described in U.S. Pat.No. 6,420,770, U.S. Pat. No. 6,406,987, U.S. Pat. No. 6,403,445, andU.S. Pat. No. 6,350,661.

Presently, using up to a 0.18 μm design rule, a contact pattern can beformed with a distance of 0.2-0.3 μm between the contact and the trenchwithout misalignment. However, as the semiconductor device becomes morehighly integrated, for example, by a 0.15 μm or 0.13 μm design rule andthe like in the future, the distance between the contact and the trenchbecomes 0.1 μm, 0.0 μm, etc, (i.e., there is no margin for the contactalignment), and the current patterning processes cannot integrate thesemiconductor device.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1 a to 1 e are cross-sectional views illustrating an examplemethod of forming a trench in a semiconductor device in accordance withthe teachings of the present disclosure.

DETAILED DESCRIPTION

In view of the foregoing, the present disclosure recognizes that thereis a need for a new structured trench and a new formation processthereof in order to realize more highly integrated semiconductordevices. Hereinafter, an example method of fabricating a semiconductordevice incorporating such a trench will be described in detail withreference to the accompanying drawings.

FIGS. 1 a to 1 e are cross-sectional views illustrating an examplemethod of forming a trench in a semiconductor device. First, as shown inFIG. 1 a, a pad oxide film 12 is thinly deposited on a semiconductorsubstrate 11. A first silicon nitride film 13 is deposited on the padoxide film 12. A photosensitive film is applied and exposed on the firstsilicon nitride film 13. A pattern is then formed in the photosensitivefilm 14 by removing only the portion (s) of the photosensitive film onthe region(s) in which the trench(es) are to be formed.

The pad oxide film 12 is optionally deposited in order to prevent orreduce stressing of the first silicon nitride film 13 from beingtransferred to the semiconductor substrate 11. The pad oxide film 12 ispreferably deposited thinly, for example, at a thickness of about100-300 Å.

Since the first silicon nitride film 13 is made of a material having ahigh selectivity over the pad oxide film 12, the first silicon nitridefilm 13 functions as a termination layer in a subsequent chemical andmechanical polishing process for a trench oxide. The first siliconnitride film 13 is preferably deposited at a thickness of about1500-3000 Å, for example, a thickness of about 2000 Å.

Although in the illustrated example, the pad oxide film 12 and the firstsilicon nitride film 13 are formed, persons of ordinary skill in the artwill appreciate that the pad oxide film 12 and the first silicon nitridefilm 13 are optional and may be not formed.

After the photosensitive film 14 is patterned, a hollow 100 is formed byetching the exposed first silicon nitride film 13, the pad oxide film12, and the semiconductor substrate 11 up to a predetermined depth usingthe photosensitive film pattern 14 as a mask. Subsequently, thephotosensitive film pattern 14 is removed, and then a cleaning processis performed.

The depth of the hollow 100 preferably corresponds to the thickness of aside wall layer to remain in a subsequent etch back process. Inconsideration of this, the hollow 100 is formed by etching thesemiconductor substrate 11 such that the depth of the hollow 100 isthinner than a desired depth of the trench.

Next, as shown in FIG. 1 b, a second silicon nitride film 15 isdeposited as a sacrificial layer on an entire surface of the firstsilicon nitride film 13 and an inner wall of the hollow 100. Next, thefirst silicon nitride film 13 and the semiconductor substrate 11 on thebottom of the hollow 100 are exposed while leaving the second siliconnitride film 15 on a side wall of the hollow 100 to form a side walllayer 15′, as shown in FIG. 1 c.

The thickness of the sacrificial layer 15 is preferably selected suchthat the side wall layer 15′ has a width of about 200-400 Å measuredfrom the side wall of the hollow 100. When viewed from an entiresectional view, the side wall layer 15′ is formed on both side walls ofthe hollow.

Subsequently, a trench 200 is formed by further etching thesemiconductor substrate 11 exposed on the bottom of the hollow 100 up tothe desired depth of the trench (see FIG. 1 c).

Next, as shown in FIG. 1 d, an insulation film 16 is thickly depositedon the entire top surface of the first silicon nitride film 13, the sidewall film 15′ and the trench.

Then, as show in FIG. 1 e, the trench isolation process is completed bychemically mechanically polishing the insulation film 16 until the firstsilicon nitride film 13 is exposed.

The insulation film 16 can be formed, for example, of an oxide film.

Before the insulation film 16 is formed, a liner oxide layer can beformed on the side wall layer 15′ and the trench. In such a case, thetrench is filled by forming the insulation film on the liner oxidelayer.

As apparent from the above description, the hollow 100 is formed byetching the semiconductor substrate first. The nitride film 15 is thendeposited on the inner wall of the hollow 100. The side wall layer 15′is then formed by etching back the nitride film 15. Subsequently, thedesired trench is formed by etching the semiconductor substrate. Becausethe side wall layer 15′ is formed on the side wall of the trench,contact spiking is prevented even in the case of misalignment of thecontact pattern. Therefore, the impossibility of realizing a highlyintegrated semiconductor device due to contact spiking can be overcome.

From the foregoing, persons of ordinary skill in the art will appreciatethat the above disclosed methods secure a process margin formisalignment of a contact pattern in order to facilitate the fabricationof more highly integrated semiconductor.

The illustrated method of forming a trench in a semiconductor devicecomprises: forming a hollow 100 by etching a portion of a semiconductorsubstrate 11; forming a side wall layer 15′ on an inner side wall of thehollow 100; forming a trench by further etching the semiconductorsubstrate 11 exposed through the bottom of the hollow; and filling thetrench by forming an insulation film 16 on the side wall layer and thetrench.

Preferably, forming the side wall layer 15′ on the inner side wall ofthe hollow 100 includes forming a sacrificial layer 15 on the hollow 100and the semiconductor substrate 11; and forming the side wall layer 15′by etching back the sacrificial layer 15 such that the sacrificial layer15 remains only on the inner side wall of the hollow 100.

Preferably, the sacrificial layer 15 is a silicon nitride film.

Preferably, the side wall layer 15′ has a width of approximately 200-400Å measured from the inner side wall of the hollow 100.

Preferably, before forming the hollow 100, a pad oxide film 12 and apolishing stop layer 13 is formed, wherein the hollow 100 is formed byetching the polishing stop layer 13, the pad oxide film 12 and thesemiconductor substrate 11.

Preferably, the polishing stop layer 13 is a silicon nitride film formedat a thickness of approximately 1500-3000 Å.

Preferably, the pad oxide film 12 is formed at a thickness ofapproximately 100-300 Å.

Preferably, in filling the trench by forming the insulation film 16 onthe side wall layer 15′ and the trench, the insulation film 16 is formedto fill the trench on the entire surfaces of the polishing stop layer13, the side wall layer 15′ and the trench, and the insulation film 16is then chemically mechanically polished until the polishing stop layer13 is exposed.

Preferably, an oxide film is formed as the insulation film 16.

Preferably, before the insulation film 16 is formed, a liner oxide layeris formed on the side wall layer 15′ and the trench, and the insulationfilm 16 is then formed on the liner oxide layer to fill the trench.

Although certain example methods and apparatus have been describedherein, the scope of coverage of this patent is not limited thereto. Onthe contrary, this patent covers all methods, apparatus and articles ofmanufacture fairly falling within the scope of the appended claimseither literally or under the doctrine of equivalents.

1. A semiconductor device comprising: a trench formed in a semiconductorsubstrate; a side wall layer formed on an inner side wall of the trench;and an insulation film formed on the side wall layer and the trench forfilling the trench.
 2. A semiconductor device as defined in claim 1,wherein the side wall layer is formed at a predetermined height from atop surface of the semiconductor substrate.
 3. A semiconductor device asdefined in claim 1, wherein a height of the side wall layer is less thana depth of the trench.
 4. A semiconductor device as defined in claim 1,wherein the side wall layer has a width of approximately 200-400 Åmeasured from the inner side wall of the trench.
 5. A semiconductordevice as defined in claim 1, wherein the side wall layer comprises asilicon nitride film.
 6. A semiconductor device as defined in claim 1,wherein the insulation film comprises an oxide film.
 7. A method offorming a trench in a semiconductor device comprising: forming a hollowby etching a portion of a semiconductor substrate; forming a side walllayer on an inner side wall of the hollow; forming a trench by furtheretching the semiconductor substrate exposed through the bottom of thehollow; and filling the trench by forming an insulation film on the sidewall layer and the trench.
 8. A method as defined in claim 7, whereinthe side wall layer has a width of approximately 200-400 Å measured fromthe inner side wall of the trench.
 9. A method as defined in claim 7,wherein the side wall layer comprises a silicon nitride film.
 10. Amethod as defined in claim 7, wherein the insulation film comprises anoxide film.
 11. A method as defined in claim 7, wherein forming the sidewall layer on the inner side wall of the hollow further comprises:forming a sacrificial layer on the hollow and the semiconductorsubstrate; and forming the side wall layer by etching back thesacrificial layer such that the sacrificial layer remains on the innerside wall of the hollow.
 12. A method as defined in claim 11, whereinthe sacrificial layer comprises a silicon nitride film.
 13. A method asdefined in claim 11, wherein the side wall layer has a width ofapproximately 200-400 Å measured from the inner side wall of the hollow.14. A method as defined in claim 7, further comprising: before formingthe hollow, forming a pad oxide layer and a polishing stop layer,wherein the hollow is formed by etching the polishing stop layer, thepad oxide layer and the semiconductor substrate.
 15. A method as definedin claim 14, wherein the polishing stop layer comprises a siliconnitride film.
 16. A method as defined in claim 14, wherein the pad oxidelayer is formed at a thickness of approximately 100-300 Å.
 17. A methodas defined in claim 14, wherein the polishing stop layer is formed at athickness of approximately 1500-3000 Å.
 18. A method as defined in claim14, wherein the insulation film is formed to fill the trench on entiresurfaces of the polishing stop layer, the side wall layer and thetrench, and the insulation film is then chemically mechanically polisheduntil the polishing stop layer is exposed.
 19. A method as defined inclaim 18, wherein the insulation film comprises an oxide film.
 20. Amethod as defined in claim 7, wherein, before the insulation film isformed, a liner oxide layer is formed on the side wall layer and thetrench, and the insulation film is then formed on the liner oxide layerto fill the trench.